Fred, about capstan move, this is again a compromising, it induce more dip, and slow the motion if overdone (and I don't speak of the lack of response + friction that is due to less good magiclining). So I agree this is very tempting and the only way to get a result on some actions, but the ideal alignment on magic line is yet the way to have the best work done at the key/whippen's path is not it ? Then if the whippen heel moves also, that is different... My cents, without really backup experience, just observations. Best Regards - Happy .... New .... Year. Isaac OLEG > -----Message d'origine----- > De : caut-bounces@ptg.org [mailto:caut-bounces@ptg.org]De la part de > Fred Sturm > Envoye : lundi 5 janvier 2004 22:01 > A : College and University Technicians > Objet : RE: Touch Weight > > > Nice summing up, David! I think what you describe should be > within the > capabilities of anyone who is replacing hammers on a > quality grand. And > certainly that should include any caut. > In cases where "original weight" hammers are > available, and reliably so, > reproducing original conditions is no problem. But hammer > weights are all > over the place. There are a lot more options available to > us now, but it > takes a lot of knowledge to select an appropriate set, and > even then there > is no guarantee, unless one has the budget and/or time to > have many sets > available. In any case, it is necessary to know how much > weight to remove > from whatever set you have (tapering and tailing) to get > good results. So > you have to have the basic abilities David describes to > come up with good > results. > I would add that an action rebuilder should also have > knowledge and > experience to use (if needed) wipp's with assist springs > (with accompanying > adjustments), and possibly to do minor capstan movement. > This is not > extraordinarily complex stuff - though you do have to be on > the ball and > skilled in precise work. But again, that _should_ describe > any caut. at > least on a good day, ;-). > Regards, > Fred Sturm > University of New Mexico > > --On Saturday, January 3, 2004 9:56 PM -0800 David Love > <davidlovepianos@earthlink.net> wrote: > > > Jim: > > > > I agree with you generally. But there are times when > modest redesigns are > > in order and to fail to consider them will often lead to > bad results. > > While a thorough understanding of design elements will > always give you a > > better result, there are some simple ways to approach > things if you don't > > yet have that type of expertise that will often give you > a better result > > than what is there. > > > > An overall look at the action before it is disassembled > can give you a lot > > of information without taking the extensive measurements > that Stanwood > > suggests. I do think it is important to adopt the > balance weight as a > > standard rather than simple downweight, but understanding > that is not > > difficult and is outlined well in one of Stanwood's > articles in the PTJ a > > few years back. (You also mentioned the formula in you > previous post.) > > )Measure the knuckle to center distance, a few sample > hammer weights (try > > measuring all the C's to give you a sense of the weight > curve), the up and > > down weights and look at the number of leads in the keys and their > > placement. That information will give you a lot with > which to make > > decisions about changes. > > > > If you don't have extensive knowledge, then the simplest > changes that can > > be made, if you think there is a problem with the action > set up, will > > involve adjusting hammer weight or selecting a > knuckle-to-center pin > > dimension that is different than the existing one. If > the old action > > weighs off where you want it to and there aren't an > excessive number of > > leads in the keys, then you can try to simply duplicate > what is there, > > weighing the hammers and following the procedures you > laid out in your > > previous post. > > > > Without weighing the front weights of the keys it is difficult to > > determine precisely what constitutes excessive front > weighting, but as a > > general rule no more than four in the low bass, three in > the low tenor, > > two in the mid treble and one in the high treble. That's > assuming they > > are placed toward the front with moderate spacing between > them. If the > > leads are placed back toward the balance rail, then you > can add one more > > lead and probably not get excessive. If your desired > hammer weights > > will cause you to have to add more leads to achieve the > balance weight > > you want, then consider using a knuckle to center > dimension that is 1 mm > > longer than the existing one. A move of the knuckle by 1 > mm will usually > > change the BW by about 5 grams ( a longer knuckle to > center pin dimension > > will also reduce friction slightly). Try a few samples > to make sure > > that they will regulate properly. If you are unable to alter the > > knuckle dimension and your existing hammers are producing > excessive > > balance weights then you will have to reduce the hammer weight. > > Depending on the action leverage, a reduction in the > hammer weight by 1 > > gram will cause a reduction in the BW of 5-6 grams, or it > will allow you > > to take one 12 gram lead out of the key from midway > between the front of > > the key and the balance rail. Not hard stuff. I use a > balance weight > > range of 36 - 40 grams (lighter - heavier). While there > are times when > > one might want to go lower or higher, I would generally > recommend staying > > in that range. I default most actions to around 38 > grams. Of course, be > > sure whatever you do that you test for regulation with > samples. It is > > likely, however, that an action that requires a modest > number of leads to > > achieve a medium balance weight will, by definition of > action ratios, > > regulate properly. > > > > These sorts of simple design changes are routinely made > and usually > > without any problems. I don't think technicians who > aren't well versed > > in action design need fear these types of changes. Just > sample things > > methodically and take care to create a smooth hammer > weight curve by > > whatever your favorite tapering system is (mine is with a > table saw). > > Though I prefer a more thorough approach as is offered by Stanwood > > methodology, you can get good results making modest > changes to the action > > without all the platforms and detailed formulas. Just > work carefully > > and think through cause and effect before you glue it all > together. > > > > > > David Love > > davidlovepianos@earthlink.net > > > > > >> [Original Message] > >> From: James Ellis <claviers@nxs.net> > >> To: <caut@ptg.org> > >> Date: 1/2/2004 4:21:11 PM > >> Subject: Touch Weight > >> > >> David Love's point is well taken, and I agree. However, > my previous post > >> titled "Touch Weight" was in response to Paul Legard's > request for a > > simple > >> routine to follow that would produce good results. From > reading some of > >> the posts on this list, it seems to me that many > technicians out there do > >> not have a sufficiently clear concept of action dynamics > to attempt any > >> sort of re-design of an existing action. Hammer weight (mass) is > >> dictated by string mass and the sound one wants to produce, but > >> constrained by the mechanical limitations of the system. > John Hartman's > >> description of > > moment > >> of inertia is correct. You must look at the entire > compound lever > >> system, but it all boils down to static weight, leverage > ratio, time, > >> mass, and distance traveled. No matter how you describe > it, the basics > >> remain the same, and it is not just "theoretical". It > is very real, and > >> provable. The simple point I am making is: If you > really know what you > >> are doing, > > go > >> ahead and re-design the action. If not, don't do it. > >> > >> Sincerely, Jim Ellis > >> > >> > >> _______________________________________________ > >> caut list info: https://www.moypiano.com/resources/#archives > > > > > > > > _______________________________________________ > > caut list info: https://www.moypiano.com/resources/#archives > > > _______________________________________________ > caut list info: https://www.moypiano.com/resources/#archives
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